1. Field of the Invention
The present invention relates to a transmitting power amplifier for collector voltage boosting mobile terminals, and specifically to a power amplifier capable of improving distortion characteristics in a linear operation region.
2. Background Art
In a mobile terminal of a CDMA (Code Division Multiple Access) or the like, a power amplifier for amplifying transmission signals is used (for example, refer to Japanese Patent Laid-Open No. 2007-81561). The power amplifier comprises amplifier transistors, matching circuits for transforming impedance before and after amplifier transistors, and a bias circuit for setting the bias points of the amplifier transistors.
The matching circuits and the bias circuit have been tuned for basic modulation used in telephone calls or the like. Conventionally, for modulation of a high peak power used in high-speed data communications other than basic modulation, the matching circuit or bias circuit has not been changed, but only the collector voltage of the amplifier transistor has been elevated.